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Dresden 2006 – wissenschaftliches Programm

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MM: Metall- und Materialphysik

MM 36: Amorphous and Liquid Materials IV

MM 36.6: Vortrag

Donnerstag, 30. März 2006, 17:45–18:00, IFW B

Positron annihilation spectroscopy of glassy Mg65Cu25Y10 ribbons — •Dirk I. Uhlenhaut1, Alberto Castellero1, Florian Dalla Torre1, Carlos Palacio2, Nikolay Djourelov2, Danny Segers2, and Jörg F. Löffler11Laboratory of Metal Physics and Technology, Swiss Federal Institute of Technology (ETH) Zürich, Wolfgang-Pauli-Str. 10, CH-8093 Zürich, Switzerland — 2Department of Subatomic and radiation physics, Gent University, Proeftuinstraat 86, B-9000 Gent, Belgium

The well-known Mg-Cu-Y amorphous alloys become brittle during quenching or ageing. The ductile state is obtained at high quenching speeds, while a low copper content delays embrittlement during room-temperature ageing. Here we report on positron annihilation spectroscopy of amorphous ribbons from the Mg65Cu25Y10 bulk glass-former, measuring positron lifetime, Doppler broadening and coincidence Doppler broadening as a function of the alloy’s room temperature age. A decrease in positron lifetime and changes in the Doppler peak width, corresponding to a reduction of free volume, were seen during the time the embrittlement takes place at room temperature. Coincidence Doppler broadening spectroscopy revealed changes in the immediate environment of the free volume during annihilation. Analogies with calorimetric measurments and mechanical tests are discussed.

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